1. Field of the Invention
The present invention relates to an apparatus and a method for release and controlled storage of desired preset amounts in a preset memory storage of a postage metering machine.
2. Brief Description of the Background of the Invention Including Prior Art
Postage meter machines operate according to the postal requirements in the respective country either according to the bill account method or according to the prepaid availability method. In the case of the prepaid availability method, if required, upon payment of a corresponding amount of money to an authorized office, for example the postmaster at a post office, the preset counter is adjusted by an amount that can be selected as desired. Thereupon the postage metering machine can be used as long as the preset amount has not been used up. Then there occurs a new requirement for another setting of the preset counter of the postage metering machine.
Thus, whenever an adjustment of the preset counter of a postage metering machine is necessary, conventionally it must be taken to the authorized office, which is cumbersome and requires considerable time.
A method and an apparatus for the remote setting of postage metering machines is known from British patent GB No. 1417872, which overcomes the recited disadvantage. According to this method, the user of the distributed and remotely stationed postage metering machine operates by telephone in conjunction with a central office. This office is equipped with a computer that calculates key words in each case from data transmitted, which include an authorization code of the user, and the authorized key value is to be sent to the postage metering machine. An electronic lock in the postage metering machine releases the predetermined amount only when the proper key code number is entered.
The security of this method with respect to unauthorized manipulations and metering without payment is based on cryptological methods known in principle, and this method appears to be sufficient for the purpose intended. However, the central location requires a computer, which means a substantial expenditure.
A method and an apparatus for securing of data transmission on an unsecured path in telephone systems is known from the Swiss patent No. 646,558, which has an equivalent in British patent No. 2,020,513. In this case, the two end points of the transmission path are each provided with an algorithm module, one of the end points in provided with a random number generator, and the other end point is provided with a comparator. Security is achieved by calculating a key number in the two algorithm modules from two starting values in each case, the key number then being compared in the comparator. One starting value is the random number generated in the random number generator, which is used in the two modules. The other starting value is an entered or, respectively, stored identification number. If the key numbers are equal, this serves as a proof for the correctness of the entered identification number.